1. Field of the Invention
The invention is directed to an improved air gap baffle for a gas cooled dynamoelectric machine which improves sealing between the rotor and the baffle of the machine.
2. Background of the Invention
Examples of gas cooled dynamoelectric machines of the type with which the present invention may be advantageously employed are disclosed in the U.S. Pat. No. 3,110,827 to Baudry and U.S. Pat. No. 3,348,081 to Willyoung. Both patents are directed to dynamoelectric machines of the type having an air-tight casing filled with a cooling gas, a stator core, a rotor defining an air gap with the stator core and means for recirculating the cooling gas through the stator and the rotor. In the Baudry patent, the means for circulating the coolant is an axial compressor mounted on one end of the rotor. In the Willyoung patent, the gas coolant is caused to flow through the rotor and the stator core due to pumping action created by the rotor itself as it scoops gas from the air gap between the rotor and the stator core. Both of the cooling systems disclosed in the Baudry and Willyoung patents require the use of annularly arranged gas segregating baffles disposed in the air gap between the rotor and the stator core. These air gap baffles are used to define air gap zones that are to be maintained at different pressures and/or are to have coolant gas flow in opposing directions. Whether air gap baffles are used to maintain a pressure differential between adjacent air gap zones, or simply used to segregate gas flow, it is desirable for the effective cooling and efficient operation of the machine to provide air gap baffles which minimize gas leakage between adjacent air gap zones.
In both the Baudry and Willyoung patents, annularly arranged stator air gap baffles are provided in radial alignment with rotor baffles which normally are non-magnetic steel rings shrunk-fit to the surface of the rotor. These stator air baffles may be constructed of an elastomeric material and are designed to provide small running clearances between the rotor and the stator core. However, a problem that limits the minimum running clearances attainable with stator air gap baffles constructed according to Baudry or Willyoung is that these stator air gap baffles are designed to be installed before the rotor is inserted in the machine. Since the rotor must be inserted after the assembly of the stator baffles, and it is impossible to insert the rotor in exact axial alignment with the openings in the stator air gap baffles, assembly clearances between the stator baffles and the rotor must be provided which allow the unimpeded insertion of the rotor without interference between the rotor and the baffles which could cause damage to either member. Thus, assembly clearances will limit the minimum running clearances obtainable with either the Baudry or Willyoung baffle designs.
Another example of a stator air gap baffle for a pressurized zone dynamoelectric machine is disclosed in U.S. Pat. No. 3,265,912 to Baudry. This second Baudry patent shows annularly arranged stator air gap baffles which are assembled from a plurality of arcuate baffle sections made of a glass melamine or glass epoxy material. The stator baffles are assembled in radial alignment with non-magnetic steel rings shrunk-fit to the surface of the rotor. With this segmented stator baffle design Baudry attempts to minimize running clearances and avoid the assembly clearance problem by providing a stator air gap baffle which is assembled after the insertion of the rotor. However, stator air gap baffles which are removable or arranged so that they can be installed or removed with the rotor in place are complex in design and expensive to manufacture and assemble.
Accordingly, it is a principal object of the present invention to provide an air gap baffle for a gas cooled dynamoelectric machine which is simple in construction and which minimizes running clearances between the baffle and the rotor.
Another object of the present invention is to provide a stator air gap baffle which improves sealing between the rotor and the baffle by reducing running clearances and providing a labyrinth seal.
Another object of the present invention is to provide a flexible air gap baffle which minimizes the possibility of damage to either the baffle or the rotor during the assembly of the dynamoelectric machine.
Another object of the present invention is to provide a flexible stator air gap baffle which allows a dynamoelectric machine to be assembled with smaller clearances between the baffle and the rotor than those obtainable with previous air gap baffle designs.
Another object of the present invention is to provide a stator air gap baffle which minimizes eddy current losses in th dynamoelectric machine.